1. Field of the Invention
The present invention relates to a robot control system, in particular, relating to a robot control system having a function of emitting warnings and stopping the operation of a machine based on the distance of the machine from a portable wireless operation panel.
2. Description of the Related Art
Portable operation panels for giving instructions and the like to a robot are required to satisfy the standard (ISO 10218-1) that the operation panel can output signals to perform an emergency stop of the robot so as to be able to promptly stop the robot in an emergency. When the portable operation panel is used based on wireless communication, there is a risk that the robot cannot be stopped promptly if the quality of the wireless communication is low, and hence is hazardous. For this reason, it has been a practice that the robot is stopped when the quality of wireless communication becomes lower than a certain level to thereby ensure safety.
However, even if the quality of communication is good, if the operator moves away from the robot, the robot can be controlled from a place where the operator cannot check, which is hazardous.
As a conventional robot control system, there has been a known system which ensures safety by recognizing the position of the operator (e.g., Japanese Patent No. 5492438). However, this is not a system that can recognize the distance of the robot from a mobile body referred to as a portable wireless operation panel.
As a wireless teaching device, there has been a known automated machine system which, by exchanging live signals by wireless communication at predetermined intervals and monitoring the time interval of reception so as to detect the wireless communication state, gives warnings to the operator and/or stops the automated machine when the wireless communication state becomes poor (Japanese Unexamined Patent Publication (Kokai) No. 2007-233817). This conventional art is based on the technology that the reception interval between live signals will become longer due to degradation of the communication state of the wireless communication when the distance between the receivers becomes far. However, this technology does not take any consideration of possible variations of the quality of communication, i.e., some places have a good quality of communication and other places with poor quality due to environmental factors.
There is another known automated machine system which, by monitoring the intensity of radio waves between the controller and the teaching device, gives warnings and/or stops the automated machine when the intensity of radio waves becomes equal to or lower than a predetermined threshold (for example, International Publication 2006/103838). FIG. 1 shows a configuration of a conventional automated machine system. A conventional automated machine system 1000 is adapted to stop a robot 1001 when the quality of communication between a transceiver 1021 of a control device 1002 for controlling the robot 1001 and a transceiver 1041 of a teaching device 1004 degrades, to thereby ensure safety. However, the teaching device 1004 can control the robot 1001 even if they are located distant from each other as long as the quality of communication is good. As a result, if the operator erroneously operates the teaching device 1004 when the teaching device is located far away from the robot 1001, the robot may move without knowledge of the operator, causing safety problems. There are many robot systems of which the robot 1001 and the transceiver 1021 of the control device 1002 are located far away from each other. A situation in which the transceiver 1021 of the control device 1002 and the transceiver 1041 of the teaching device 1004 are located close to each other and hence communication quality is good even if there is a great distance between the teaching device 1004 and the robot 1001 can be easily imagined.